Plate filter

ABSTRACT

A plate filter press includes a plurality of face-to-face arranged filter plates movable into open and closed positions. Any two adjoining filter plates together define a filter chamber bounded by a continuous, raised sealing edge carried on at least one of the two adjoining filter plates. Separate heavy liquid intake members constituted by tubular bars are in fluid communication with each filter chamber. The sealing edges are provided with a respective recess extending in a longitudinal direction of the sealing edges. The tubular bars extend in the longitudinal direction and are sealingly received in the respective recesses in the closed position. Each tubular bar has a liquid outlet opening, and each sealing edge is provided with a transverse liquid passage situated between the recess and the filter chamber. The transverse liquid passage is oriented transversely to the longitudinal direction and is in a fluid communication with the liquid outlet opening of the tubular bar seated in the recess for maintaining a fluid communication between the tubular bar and the filter chamber.

BACKGROUND OF THE INVENTION

The invention relates to a plate filter equipped with a plurality offilter plates that are movable by means of a closing device so as to bepressed against one another, with two adjacent filter plates in eachcase being in communication with one another by way of opening spacersand forming a filter chamber which is delimited by a continuous, raisedsealing edge at at least one of the filter plates. At least one heavyliquid intake opens into the filter chamber and at least one of thefilter plates delimiting the respective filter chamber is provided witha press membrane that can be charged by pressure medium. A preferablyband-shaped filtering means is also provided which extends between eachpair of adjacent filter plates.

In order to realize a large chamber volume and thus the correspondinglylarge cake thickness in plate filters of the above-described type, it isnecessary to either configure the filter plates in the shape of a pot,in which case the bottom of the pot is formed by the press membrane andthe filter surface is formed by the next-following filter plate disposedopposite the pot membrane and delimiting the filter chamber on the otherside, as this is disclosed, for example, in German Patent DE 1,461,500.However, such a filter plate configuration has the drawback that, on theone hand, it has only one filter surface and, on the other hand, can beconstructed only with the filter plates in the known horizontalarrangement since only with a horizontal arrangement of the filterplates the cake can be removed at the end of the filtration process.

In order to realize an increase in filter output in such plate filters,the filter plates have been designed to be effective bilaterally and thefilter surface area has been enlarged in that a cake frame was placedbetween each pair of filter plates. The drawback of such cake frames isthat it is not ensured, when the press is opened, that the filter cakedrops out immediately and is transported completely out of the filterchamber by the filter band drawn through it. Remainders of filter cakethat drop down later may remain lying on the filter band in the regionof the sealing faces which leads to leakages in the entire system.Moreover, such cake frames require a high fill level so that thecirculating filter band and the membranes or the membrane plates are notdestroyed when pressure is applied. This can be realized only witheasily filtrable suspensions. Finally, the provision of a cake framerequires very high closing forces so that a sufficiently high clampingforce is applied to the cake frame which otherwise would be widenedoutwardly by the pressure of the suspension, leading to leakages andthus to malfunction of the entire press. The heavy liquid intake in suchbilaterally filtering filter chambers would inevitably have to occur byway of the cake frame disposed between the two filter surfaces as thiscan be found, for example, in German Patent DE 2,043,156.

SUMMARY OF THE INVENTION

It is now the object of the invention to provide a plate filter of theabove-mentioned type which permits the arrangement of two filtersurfaces per filter chamber even without the use of cake frames.

This is accomplished according to the invention in that at least onesealing edge at each pair of adjacent filter plates is given a recess inits edge into which a tubular body extending in the direction of thesealing edge can be placed in a sealing manner as the heavy liquidintake. This tubular body is provided with heavy liquid dischargeopenings which open into the filter chamber. The individual tubularbodies of the filter plate packet formed by the filter plates areconnected with opening spacers that engage at the individual filterplates. This arrangement makes it possible to design plate filters withvertically oriented filter plates as well as with horizontally orientedfilter plates. The filtering means may here be designed, particularlyfor filter plates that are oriented horizontally, as an endless bandwhich is brought through the entire filter plate packet either in zigzagform or it encloses each filter plate between itself in the form of anendless band. Since the two filtering-means which lie on mutually facingfilter plate surfaces are sealingly pressed against one another from thesealing edge when the filter plate packet is closed, the solutionaccording to the invention makes it possible to introduce the heavyliquid to be filtered between the two filtering means which delimit thefilter chamber on both sides. One, but also both of the mutually facingfilter faces may be given a pot shape if the sealing edge is given theappropriate height and may be provided with a press membrane on whichthe filtering means rests. The tubular body serving as the heavy liquidinlet is now sealingly placed into a recess disposed at the sealing edgeof a filter plate advisably, however, symmetrically to the parting linein mutually contacting sealing edges and is held in a sealing mannerwhen the filter plate packet is pressed together. On its exteriorperiphery the tubular body may here be provided with a separate sealingmeans, for example in the form of an 0-ring, or it may be provided as awhole with a rubber coating so that a proper seal against the filterchamber is ensured. Due to the fact that the tubular body which servesas the heavy liquid inlet is connected with the individual filter platesby way of opening spacers, as this is known, for example, for cakeframes, it is ensured that the tubular body, when in the open state, isspaced from the sealing edge so that the filter band is able to passthrough freely and the resulting filter cake can be discharged properly.At the same time, it is ensured that the tubular body is always heldaccurately with reference to the recess in the sealing edge.

Since, particularly in plate filters equipped with a movable filterband, the filter plates are configured as squares or rectangles, thetubular body serving as the heavy liquid intake may be arranged, withrespect to the direction of movement of the filter band, at the sealingwall opposite the discharge end of the filter chamber and/or, withrespect to the direction of movement of the filter band, at bothlongitudinal sides of the filter plate. The tubular body may here extendover only part of the length of the respective plate side.

As an advantageous feature of the invention it is provided that thetubular body extends essentially over the width of the filter plate.This arrangement has the advantage that the heavy liquid does not enterthe filter chamber in a "dot shape" but over the entire width of thefilter chamber so that, if the heavy liquid discharge opening of thetubular body is dimensioned accordingly, the heavy liquid is able toenter the filter chamber at a slow flow rate even for large throughputquantities, thus preventing the filter surfaces in the entrance regionfrom being washed free. Another advantage of this embodiment is thatsuch a tubular body, which extends over the entire width of the filterplate, can be brought out of the press in a simple manner and can beconnected with the appropriate hose conduits for the heavy liquidintake. This applies for an arrangement on the side of the filterchamber opposite the cake discharge as well as for a lateral arrangementwith respect to the passage of the band. Such a configuration of thetubular body permits, as a further advantageous feature, the recess inthe sealing edge to be formed as a longitudinally extending groove. Thisresults in precisely definable geometric relationships which simplifythe sealing process.

As a further feature of the invention it is provided that the pressmembrane, which is connected with the filter plate, is thickened alongits edge and forms the sealing edge. This configuration makes itpossible to produce filter plates having an integrated press membrane,as they are known, for example, for plastic filter plates, or filterplates in which the membrane is welded onto a basic plate body. In thisconnection it is advisable, as a further feature of the invention, toarrange the recess for accommodating the tubular body in the portion ofthe sealing edge of the press membrane near the filter chamber. Thisensures proper sealing of the filter chamber. This configuration isparticularly advantageous if the tubular body extends essentially overthe entire width of the filter plate. Particularly in connection with atubular body that extends over the entire width of the filter plate itis advisable for the tubular body to be deformable transversely to itslongitudinal extent so that, under the influence of the closingpressure, the tubular body is able to be deformed in the same manner asthe sealing edge.

As a further feature of the invention it is provided that the groove forreceiving the tubular body is disposed with its edge adjacent to theexterior of the sealing edge of the press membrane in the edge of thefilter plate. This arrangement has the advantage that the groove forreceiving the tubular body is removed from the critical zone immediatelyat the edge of the filter chamber so that the sealing edge remainsunweakened in this region and a proper seal is ensured. To accomplishthis, it is merely necessary for the mutually associated sealing edgesof oppositely disposed filter plates to be provided with grooves which,when the filter chamber is closed, are flush with the heavy liquiddischarge openings of the tubular body. The tubular body itself mustproperly seal the gap in these regions when the filter chamber isclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail for embodimentsthereof which are illustrated in schematic drawing figures, in which:

FIG. 1 depicts a plate filter having horizontally oriented filterplates;

FIG. 2 depicts a plate filter having vertically oriented filter plates;

FIG. 3 depicts a first embodiment of a heavy liquid

intake for a plate filter according to FIG. 1;

FIG. 4 is a top view of the heavy liquid intake of FIG. 3;

FIG. 5 depicts a first embodiment of a heavy liquid intake for a platefilter according to FIG. 2;

FIG. 6 is a vertical sectional view of a second embodiment of a heavyliquid intake for plate filters according to FIGS. 1 and 2;

FIG. 7 is a vertical sectional view of another configuration of theembodiment of FIG. 6;

FIG. 8 depicts a modification of the embodiment of FIG. 7;

FIG. 9 is a top view of the configuration of FIG. 8 in the form of aso-called box-shaped inlet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiment shown in FIG. 1 depicts a so-called automatic filterpress in the open state. Here, several filter plates 4 are arranged in amachine stand 1 between two end plates 2 and 3. End plates 2 and 3 hereform part of the stand, with end plate 3 being fixed to the stand whileend plate 2 is movable relative to end plate 3 with the aid of apreferably hydraulically configured closing device 6. The surfaces ofend plates 2 and 3 lying between end plates 2 and 3 and facing filterplates 4 are here configured as filter chamber walls, that is, they areprovided with channels for the discharge of filtrate or also with anappropriately channelled press membrane. By way of opening spacers 5,the individual filter plates 4 are suspended in the manner of a chainfrom the upwardly movable end plate 2 so that lifting of end plate 2causes the individual filter chambers to open successively beginning atthe top.

A band-shaped filtering means 7 is brought in a zigzag arrangementthrough the packet of filter plates so that each filter plate is coveredwith filtering means on both sides. The endless filter band 7 is hereguided in the customary manner over reversal and drive rollers and, ifthe filter plate packet is open, is pulled in the direction of the arrow8 through the filter plate packet so that the filter cake resting on thefilter band is ejected to one side from the plate filter (arrow 9). Theportion of the filter band 7 pulled out of the filter plate packet atthe bottom is conducted through a washing device 10 and back into thefilter plate packet at the top.

FIG. 2 show the arrangement of a plate filter having vertically orientedfilter plates, likewise in the open position. The structure essentiallycorresponds to the embodiment of FIG. 1 so that the same referencenumerals have been employed for the same components. However, in platefilters having vertically oriented filter plates, the end plate 3, whichis fixed to the stand, is connected by way of two lateral tension rods11 with the closing device 6 that is likewise fixed to the stand so thatthe movable end plate 2 and filter plates 4 are guided by laterallyarranged contact tabs 12 to rest on tension rod 11. By way of openingspacer means 5 which are constructed in a similar manner as those in theembodiment of FIG. 1, care is again taken that, when the filter platepacket is opened, the individual filter chambers are open successivelyand are spaced at the same distance from one another. In this embodimentas well, an endless filter band 7 is again provided which is guided bycorresponding drive and reversal rollers through a washing device 10 andin a zigzag pattern through the plate packet.

In the embodiment of FIG. 1 as well as in the embodiment of FIG. 2 it ispossible, instead of guiding the filter band through the entire filterplate packet in a zigzag pattern, to provide an endless filter band thatis associated with each filter plate and encloses merely that one filterplate. In a plate filter having vertically oriented filter plates, it isadditionally possible to employ, instead of a movable filter band,filter cloths that are fixed to the filter plates since the removal ofthe cake is then possible also by gravity, supported by the pressmembrane. The filter cloth is here, if necessary, cleaned in a separatewashing device which is introduced between a pair of plates when theplate packet is opened and sprays them off.

The heavy liquid intake into a chamber delimited by two adjacent filterplates 4 can now be effected in two different ways. In oneconfiguration, the individual filter plates are each provided with oneor more bores in the region of the sealing edge. If the plate packet ispushed together, these bores form a flow channel from which otherchannels branch off that extend in the sealing edge of each individualfilter plate and open into the filter chamber. In another embodiment ofthe plate filters, it is customary to provide channels that extend inthe sealing edge in the plane of the plate and that are brought to theoutside and are there each connected with the heavy liquid inlet bymeans of an intake hose.

If now both plate surfaces that delimit a filter chamber in a platefilter as shown in FIGS. 1 and 2 are to be provided with a pressmembrane and with a filtering means in order to double the filtersurface, the above described conventional solution of the heavy liquidintake is no longer possible. FIG. 3 shows an embodiment for anarrangement of a heavy liquid channel that extends in the plate bodyitself which solves the problem of the heavy liquid intake into such afilter press chamber with doubled filter surface. As shown in FIG. 3,each filter plate 4 has a sealing edge 13, which is raised to both sidesrelative to plate body 14, so that, with the plate packet pushedtogether, a filter chamber is formed in each case. In the embodimentshown in FIG. 3, filter plate 4 is provided with an integrated pressmembrane 15, that is, press membrane 15 is connected with the plate inone piece. A pressure medium conduit, not shown in detail here, for thesupply of water or air as the pressure medium here opens into the space16 between plate body 14 and press membrane 15 so that press membrane15, when charged with pressure medium, is pushed into the filter chamberand a filter cake disposed therein can be pressed out.

Filter plate 4 is either provided, as shown here, with an eye-shapedattachment 17 at its outer edge which forms a continuous flow channelwith a bore 18 when the plate packet is pushed together. However, bore18 may also be disposed in the sealing edge in a broadened region in acorner of the filter plate.

Each filter plate is now provided with a recess 19 at its sealing edgethrough which, with the plate packet pushed together, a tubular body 20is able to project from the outside into the filter chamber, with thetubular body being sealed by way of a sliding member 21 against thebores 18 of two adjacent filter plates and being guided in a mannersecure against rotation. Tubular body 20 is in communication withsliding tube member 21 by way of an opening 22 and its other end whichextends into the filter chamber is preferably provided with a pluralityof juxtaposed heavy liquid discharge openings 23.

As indicated by the top view of FIG. 4, the tubular body 20 of thisembodiment is given a box shape and extends only over a partial lengthof a sealing edge side between two filter plates. The ends 24 of tubularbody 20 which extend in the direction of the extent of sealing edge 13are here rounded so that, as will be described in greater detail below,the filter cloth is able to lie in close contact without being overlystretched. Several such box-shaped tubular bodies 20 may be provided foreach filter chamber formed of two adjacent filter plates.

As shown in FIG. 3, the filter cloth 7 which serves as the filteringmeans and is brought through the filter plate packet perpendicularly tothe plane of the drawing, is pulled out beyond sealing edge 13 so thatit also covers recesses 19. If now the plate packet is pushed together,tubular body 20 is pressed uniformly into recesses 19 and thussimultaneously presses the filter cloth against corresponding seals 26which, extending over the periphery of the entire sealing edge, providea seal for the gap between two adjacent filter plates. Tubular body 20is here provided with a corresponding counter-seal 27, as shown, or itis provided with a rubber coating over its entire surface which, incooperation with seal 26, ensures tightness.

FIG. 5 shows a modification of the embodiment of FIGS. 3 and 4. Here,instead of a tubular attachment to the filter plate itself, the tubularbody 20, which otherwise is configured in the same way as shown in FIG.4, is provided with a pipe connection 28 for the connection of a hose.Tubular body 20 is here connected with a holding body 29 which isprovided with two long holes 30 that extend in the direction of movementof filter plates 4 and are brought through screw bolts 31 for fasteningto filter plates 4. Additionally, tubular body 20 is connected, by wayof an opening spacer means 32 that is configured in the manner of a linkchain, with the tubular body of the respectively adjacent filter chamberso that opening of the filter chamber, which is shown closed in FIG. 5,causes tubular body 20 to be again disposed at the same distance fromboth filter plates, as shown in FIG. 3, so that the filter cloth can bepulled through.

FIG. 6 shows a particularly advantageous embodiment in a partialvertical sectional view. In this embodiment, a tubular body 33 isprovided which is inserted in a corresponding recess in the sealing edge34 of a press membrane 36 that has been glued onto a basic plate body35. Recess 37 here extends over the entire width of the filter plate sothat it is open on the sides at both ends. At one end or at both ends,the inserted tubular body is connected with the heavy liquid intake byway of appropriate hose connections. The two ends of tubular body 33which laterally project from the filter plate are again connected withone another by way of spacers so that, if the filter plate packet isopen, the tubular body is held in the center plane of the space betweentwo filter plates.

Tubular body 33 is provided with heavy liquid intake openings 38 whichopen into the filter chamber disposed between the two press membranes36. If a heavy liquid connection is provided only at one end of tubularbody 33, the heavy liquid intake openings 38 are advisably provided indifferent sizes over the length of the tubular body, with the smallerpassage cross sections being provided directly in the intake regionwhile the largest passage cross sections are provided at the end. Thus auniform heavy liquid intake is realized over the length and over theentire width of the filter chamber. Since the sealing edge of filterplate 4 is formed by a thickened portion of the membrane, and thus islikewise slightly deformable in view of the deformability of membranecomponent 36, a likewise deformable material is advisably selected fortubular body 33 so that, upon compression of the filter plate packet,tubular body 33 is also slightly deformable transversely to itslongitudinal extent. The web-shaped portion 39 which delimits recess 37toward the filter chamber here serves simultaneously as a sealing lipagainst the interior pressure in the filter chamber and improves theseal in this region. In deviation from the circular cross section, thecross section of tubular body 33 may here also be oval so as to adapt itto the thickness of the plate and, more precisely, to the thickness ofthe sealing edge formed by the membrane so as to increase the passagecross section of the tubular body itself. Thus it is possible here,without adversely affecting the structural height, to realize a largerflow cross section. The above illustrated and described embodiment of atubular body that extends over the entire width of a filter plate mayalso be employed in the solid plastic filter plate described inconnection with FIG. 3 in which the press membrane is connected in onepiece with the plate body.

In order to now not have to weaken the sealing edge 34 of the welded-onpress membrane by such a recess, FIG. 7 shows a modification of theembodiment of FIG. 6. In this embodiment, a thickened edge 34 of thepress membrane 36 is provided with a plurality of transverse grooves 40which correspond with the heavy liquid discharge openings 38 of atubular body 41 that is arranged to extend from the outside into arecess 42 that is wedge-shaped when the filter plates are pushedtogether. By shaping recess 42 in a corresponding manner in the regionof the outer edge, it is here possible to accomplish that, if theindividual filter plates are pushed together under the influence of theclosing forces, the correspondingly wedge-shaped tubular body 41 issealingly pressed in the direction toward the filter chamber against theobliquely extending sealing edge 43 of thickened edge 34. In thisembodiment as well, the individual tubular bodies 41 are spaced by meansof corresponding opening spacers 32 so that their center positionrelative to the adjacent filter plate is maintained accurately.

The tubular bodies of the embodiments of FIGS. 3 and 5 as well as thetubular bodies of the embodiment of FIGS. 6 and 7 must be disposed atthe two long sides of the respective filter plate with respect to thepassage of filter band 7. If, in an embodiment according to FIGS. 3 and4, tubular bodies are provided that extend only over part of the lengthof the sealing frame, with the filter cloth also being deformed by therecess in the sealing frame, then if only one heavy liquid inlet isprovided, a "blind insert" must be provided on the opposite side of theframe so as to obtain a uniform expansion of the filter cloth. The samealso applies if two elongate tubular bodies that extend over the fullside length of a filter plate, as shown in FIG. 6, are provided.

An elongate tubular body in the embodiment of FIG. 6 or 7, additionallymakes it possible to provide the inlet on a side edge of the filterplates that lies transversely to the direction of movement of the filterband since the associated hose connections can be brought out on thesides. Here, in consideration of a free discharge of the cake, it ismerely necessary to arrange such a tubular body at the long edge of thefilter plate disposed opposite the cake discharge side. This isindicated in FIGS. 1 and 2 by the reference numeral 33 in parenthesis.

The modification of FIG. 7 shown in FIG. 8 depicts an asymmetricalconfiguration of recess 42 in the region of the exterior border ofsealing edge 34. Here recesses 42 and transverse grooves 40 that areassociated with the heavy liquid discharge openings 38 in tubular body41 are each disposed only on one side of the filter plate.

The arrangement according to FIGS. 7 and 8 may be employed forcontinuous, rod-shaped as well as for short tubular bodies 41 thatextend only over part of the length of the sealing edge. FIG. 9 showssuch a short configuration in a top view seen in direction A withrespect to FIG. 8. The solid lines show the corner region of a filterplate 4 with its sealing edge 34 and transverse groove 40 which opensinto a chamber delimited by two adjacent filter plates.

The associated tubular 41 body on top thereof when seen from the frontis shown in dash-dot lines, with the regions of filter plate 4 and ofsealing edge 34 hidden by tubular body 41 being shown in dashed lines.The inlet opening 38 opens against the sealing edge of the adjacentplate so that the enforced deflection of the incoming heavy liquidproduces a broadening of the stream.

As can be seen in FIG. 9, in this embodiment the tubular body 41 extendsonly over a short partial length of sealing edge 34 and only in thecorner region. Thus, such inlets may be arranged in two corners, or alsoin all four corners.

However, the embodiment discussed in connection with FIG. 8 may also beemployed for through-going, rod-shaped tubular bodies. In that case,transverse grooves 40 are each associated with a passage opening 38.

In the embodiments according to FIGS. 5, 6, 7, 8 and 9, the heavy liquidis introduced in each case from a central supply pipe 44 by means ofhose connections 45 that branch off therefrom, as this is shown in FIG.7 by the bold dot-dash lines.

In the embodiment according to FIG. 7 as well as in the embodimentaccording to FIG. 8, the individual tubular bodies 41 of automaticfilter presses equipped with horizontally oriented filter plates asshown in FIG. 1 may each be suspended, by way of vertical slide andspacer pins, from the respectively upper filter plate. Thus each filterplate and its associated tubular bodies forms an independent, closedflush system when the filter plate packet is opened and closed.

We claim:
 1. In a plate filter press including a plurality offace-to-face arranged filter plates, any two adjoining filter platestogether defining a filter chamber bounded by a continuous, raisedsealing edge carried on each of said two adjoining filter plates, aseparate heavy liquid intake member being in fluid communication witheach filter said chamber, a pressing membrane provided on each of saidtwo adjoining filter plates and positioned to traverse the filterchamber, each said membrane defining a said raised sealing edge, afilter element positioned to traverse each filter chamber, means formovably supporting the filter plates, closing means for moving thefilter plates toward one another into a mutually contacting, closedcondition and for moving the filter plates away from one another into aseparated, open position, spacer means stringing the heavy liquid intakemembers to one another for supporting the heavy liquid intake members insaid open position, wherein the improvement comprises:each said liquidintake member is a tubular body; adjacent ones of said sealing edgesdefine a respective wedge shaped recess extending in a longitudinaldirection of the sealing edges; the tubular bodies extending in saidlongitudinal direction and being sealingly received in the respectiverecesses in said closed position; each said tubular body having aplurality of liquid discharge openings spaced apart from one another insaid longitudinal direction and facing said recess; each said sealingedge being further provided with a plurality of transverse groovessituated between said recess and a respective said filter chamber; saidtransverse grooves being oriented transversely to said longitudinaldirection and being in fluid communication with respective ones of saidliquid discharge openings of a respective said tubular body seated in arespective said recess for maintaining fluid communication between thetubular body and the filter chamber.
 2. A plate filter press as definedin claim 1, wherein said filter plates have a plurality of sides eachhaving a length dimension; each said tubular body extending along afilter plate side and substantially corresponding to said lengthdimension.
 3. A plate filter press as defined in claim 1, wherein saidpressing membrane has a thickened edge; said thickened edge comprisingsaid sealing edge.
 4. A plate filter press as defined in claim 3,wherein said transverse grooves are provided in said thickened edgeadjacent the filter chamber.
 5. A plate filter press as defined in claim3, wherein said recess borders said thickened edge of said pressingmembrane and is provided in an edge region of the filter plate.